An ELIT includes voltage sources (1101), switches (1102), a first set of electrode plates (1110) aligned along a central axis, and a second set of electrode plates (1120) aligned along the central axis with the first set. A first group of plates (310, 320; 810, 820) of the first set and the second set is positioned to trap ions within a first path length (340, 940). A second group of plates (410, 420) of the first set and the second set is positioned to trap ions within a shorter second path length (440, 1040). The switches select the first path length by applying voltages from the voltage sources to the first set and the second set that cause the first group of plates to trap ions within the first path length. Alternatively, the switches can select the second path length by applying voltages that cause the second group of plates to trap ions within the second path length.

A mass spectrometer is operated to simultaneously measure precursor and production data over a number of acquisitions. For each acquisition, the following steps are performed. Ion transfer optics inject ions from an ion beam into an ELIT causing the ions to oscillate axially between two electric fields produced by two the sets of reflectrons. The ELIT measures a time domain image current of the oscillating ions from ion injection to a total acquisition time, Tacq1, and fragments the oscillating ions at one or both turning points of the oscillating ions adding product ions to the oscillating ions. The fragmentation is performed at a delay time relative to the ion injection that is increased by a time increment in each subsequent acquisition making the fragmentation dependent on ion position. The measured time domain image current is stored as a row or column of a two-dimensional matrix.

A method for determining a compensation factor parameter, c, for controlling an amount of ions ionised that are injected from an ion storage unit into mass analyser, where c is an adjustment factor that is applied to optimized injection times that are based on an optimized visible charge of a reference sample, the method comprising: detecting at least one mass spectrum for at least one amount of injected ions; determining from the at least one detected mass spectrum, a slope, s(sample), of a linear correlation of a relative m/z shift with visible total charge Q.sub.v of detected mass spectra; determining the compensation factor c as c=s(reference)/s(sample) where s(reference) is the slope of a linear correlation between reference-sample relative m/z shift values and reference-sample visible charge values determined from a plurality of mass spectra detected from a plurality of respective pre-selected amounts of a clean reference sample.

One or more ions are received along a central axis through a first set of reflectron plates of an ELIT. Voltages are applied to the first set of plates and to a second set of reflectron plates in order to trap and oscillate the one or more ions. A first induced current is measured from a cylindrical pickup electrode between the first set of reflectron plates and the second set of reflectron plates. A second induced current is measured from one or more plates of the first set of reflectron plates. A third induced current is measured from one or more plates of the second set of reflectron plates. The first measured induced current, second measured induced current and third measured induced current are combined to reduce higher order frequency harmonics of the induced current.

The present invention comprises novel methods of continuously monitoring the performance of an atmospheric pressure ionization (API) system. The methods of the invention allow for improved quality monitoring of the processes that leads to the formation of ions at atmospheric pressure. The methods of the invention further allow for continuously monitoring for the quality of the ion formation process in API without the addition of extraneous material (such as labelled compounds or control known compounds) to the system being monitored.

A CDMS may include an ELIT having a charge detection cylinder (CD), a charge generator for generating a high frequency charge (HFC), a charge sensitive preamplifier (CP) having an input coupled to the CD and an output configured to produce a charge detection signal (CHD) in response to a charge induced on the CD, and a processor configured to (a) control the charge generator to induce an HFC on the CD, (b) control operation of the ELIT to cause a trapped ion to oscillate back and forth through the CD each time inducing a charge thereon, and (c) process CHD to (i) determine a gain factor as a function of the HFC induced on the CD, and (ii) modify a magnitude of the portion of CHD resulting from the charge induced on the CD by the trapped ion passing therethrough as a function of the gain factor.

There is disclosed a method for eliminating an added crosstalk signal from a measured data signal, which is generated by an image current. There is further disclosed a signal processing unit for carrying out the method. There is still further disclosed a mass spectrometer and a mass analyser comprising the signal processing unit for carrying out the method. There is yet still further disclosed a Fourier transform mass spectrometer configured to eliminate the added crosstalk signal from a measured data signal.

A device for detecting charged particles includes a substrate, a charge detection plate and an integrated circuit unit that are electrically connected together and respectively disposed on non-coplanar first and second sides of the substrate, and an interference shielding unit substantially enclosing the charge detection plate and the integrated circuit unit in such a manner as to permit impingement on the charge detection plate by the charged particles from outside of the interference shielding unit. The integrated circuit unit disposed on the second side is non-coplanar with the charge detection plate disposed on the first side so as to prevent interference on the integrated circuit unit by the charged particles.

Methods for confirming charged-particle generation in an instrument are provided. A method to confirm charged-particle generation in an instrument includes providing electrical connections to a charged-particle optics system of the instrument while the charged-particle optics system is in a chamber. The method includes coupling an electrical component having an impedance to charged-particle current generated in the chamber. Moreover, the method includes measuring an electrical response by the electrical component to the charged-particle current. Related instruments are also provided.

The user specifies regions of interest (ROIs) such as a region where a large amount of compound to be identified is estimated to be included and a region where the compound is overlapped with another compound on one or more specific MS images, and specifies addition or subtraction of the ROIs. For each of the specified ROIs, an average MS/MS spectrum is calculated from MS/MS spectrum data at measurement points in the regions, and the average MS/MS spectra at the ROIs are subjected to addition or subtraction, to obtain an MS/MS spectrum. By addition between the ROIs, the intensity of peak derived from the target compound can be increased. By subtraction between the ROIs, a peak derived from the other compound overlapped with the target compound can be removed. When the MS/MS spectrum after addition or subtraction is subjected to library search for identification, a score indicating the similarity of the spectrum is higher than the conventional score, and the identification accuracy can be improved.